It is the usual practice in present-day dental offices to use a number of separate handpieces which are driven at high speeds by compressed air. In many instances, the high speed air driven instruments also emit a spray of water with the drive air as a coolant; and it may also be controlled to emit pressurized air for cooling purposes, or other gases. It is the common practice in the prior art for such handpieces to be supported on individual brackets which, in turn, are mounted on a console adjacent to the dental chair. Compressed air and pressurized water are supplied to the various handpieces in the prior art equipment through individual tubes. The air and water are obtained from the usual mains, and the flow thereof to the console is usually controlled by foot-operated valves. In the prior art, additional valves are provided in the console so that the flow of the pressurized air and water to the individual handpieces may also be controlled. With such prior art equipment, the dentist causes the air and water to be supplied to the console by actuating his foot-operated valves; and he then causes the air or water, or both, to be supplied to a selected handpiece, by actuating appropriate valves in the console.
The valves in the prior art consoles, in addition to being complex and expensive, are difficult to operate, and they often require both hands of the dentist to control them. The control unit of the present invention, on the other hand, provides an improved valve assembly for distributing the pressurized air and water to the various dental handpieces associated with the console, and this is achieved in such a manner that the selected handpiece may be activated, as it is selected by the dentist. It will also become evident as the present description proceeds that although the pinch valve control unit of the present invention is described in conjunction with a dental handpiece, it has wider application in the art wherever the flow of fluid through a supply tube is to be controlled.
U.S. Pat. No. 3,755,899 which issued Sept. 4, 1973 to the present inventor describes apparatus in which each dental handpiece is supported in a holder on a pivotally mounted arm, and each arm includes a pinch block at one end which pinches a corresponding flexible tube to prevent the flow of fluid to the handpiece when the holder is in its down position, but which permits the flow of fluid through the tube to the selected handpiece when the holder is in its up position. Therefore, in using the apparatus described in the patent, the dentist first selects a particular handpiece from its holder, and he then flips the holder to its up position so as to activate the handpiece.
The control unit of the present invention has certain advantages over the control unit described in the prior patent referred to above in that it is less expensive to construct, and in that it operates by the insertion and withdrawal of the handpiece from the bracket and there is no need to tilt the bracket. Also, the control unit of the present invention is capable of performing certain functions beyond the capabilities of the control unit of the aforesaid patent, as will be described.
The control unit of the invention is reliable in operaton, and it is not subject to excessive wear. Whenever a tube controlled by the unit shows any evidence of wear, it is merely necessary to shift the tube so that a new portion thereof is pinched by the unit. The unit of the invention also provides a complete separation of the air and water controls which enhances its reliability. The unit of the invention is also advantageous in that it is flexible, and can be constructed to perform more or less multiple functions depending upon the particular installation.
As will be described in detail herein, the control unit of the invention makes use of resilient metal strips which, for example, may be formed of beryllium, and which act as pinch valves. Swell tubes are also used in the unit in certain of its embodiments, as will be described, to provide a delayed actuation of certain of the resilient strip pinch valves. For example, the control unit may provide for the introduction of water or coolant air to the handpiece only after the handpiece has come up to speed, and this function is controlled by the swell tube. As mentioned above, the control unit may also incorporate a "suck-back" function in the water line to prevent dripping after the handpiece has been replaced in the bracket.